U.S. patent application number 16/244452 was filed with the patent office on 2020-07-16 for magnetic field sensor using mr elements for detecting flux line divergence.
This patent application is currently assigned to Allegro MicroSystems, LLC. The applicant listed for this patent is Allegro MicroSystems, LLC. Invention is credited to Paul A. David, Jeffrey Eagen, Andrea Foletto, Remy Lassalle-Balier.
Application Number | 20200225020 16/244452 |
Document ID | / |
Family ID | 71517464 |
Filed Date | 2020-07-16 |
![](/patent/app/20200225020/US20200225020A1-20200716-D00000.png)
![](/patent/app/20200225020/US20200225020A1-20200716-D00001.png)
![](/patent/app/20200225020/US20200225020A1-20200716-D00002.png)
![](/patent/app/20200225020/US20200225020A1-20200716-D00003.png)
![](/patent/app/20200225020/US20200225020A1-20200716-D00004.png)
![](/patent/app/20200225020/US20200225020A1-20200716-D00005.png)
![](/patent/app/20200225020/US20200225020A1-20200716-D00006.png)
![](/patent/app/20200225020/US20200225020A1-20200716-D00007.png)
United States Patent
Application |
20200225020 |
Kind Code |
A1 |
Lassalle-Balier; Remy ; et
al. |
July 16, 2020 |
MAGNETIC FIELD SENSOR USING MR ELEMENTS FOR DETECTING FLUX LINE
DIVERGENCE
Abstract
Methods and apparatus for s sensor having magnetic field sensing
elements coupled in a differential bridge and a signal processor
configured to receive signals from the bridge to determine a
distance from the magnetic field sensing elements to a magnet from
flux line divergence of magnetic flux generated by the magnet.
Inventors: |
Lassalle-Balier; Remy;
(Bures sur Yvette, FR) ; Eagen; Jeffrey;
(Manchester, NH) ; Foletto; Andrea; (Annecy le
Vieux, FR) ; David; Paul A.; (Bow, NH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Allegro MicroSystems, LLC |
Manchester |
NH |
US |
|
|
Assignee: |
Allegro MicroSystems, LLC
Manchester
NH
|
Family ID: |
71517464 |
Appl. No.: |
16/244452 |
Filed: |
January 10, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01B 7/14 20130101; G01R
33/091 20130101 |
International
Class: |
G01B 7/14 20060101
G01B007/14; G01R 33/09 20060101 G01R033/09 |
Claims
1. A sensor, comprising: magnetic field sensing elements coupled in
a differential bridge; and a processing module configured to
receive signals from the bridge to determine a distance from the
magnetic field sensing elements to a magnet from flux line
divergence of magnetic flux generated by the magnet, wherein an
output signal corresponding to the determined distance from the
magnetic field sensing elements to the magnet is substantially
linear for a given airgap range.
2. The sensor according to claim 1, wherein the magnetic field
sensing elements comprise MR elements.
3. The sensor according to claim 1, wherein the magnetic field
sensing elements comprise GMR elements.
4. The sensor according to claim 1, wherein the magnetic field
sensing elements comprise Hall elements.
5. The sensor according to claim 1, further including a die,
wherein the magnetic field sensing elements are positioned in
relation to the die.
6. The sensor according to claim 5, wherein the magnetic field
sensing elements are located in a plane.
7. The sensor according to claim 5, wherein the bridge element
comprise elements L1, L2, R1, R2, and an output signal comprises
combining signals from L1, L2, R1, R2.
8. (canceled)
9. The sensor according to claim 1, wherein the magnetic field
sensing elements comprise first, second, third, and fourth MR
elements coupled in a bridge, wherein the first and second MR
elements are located in proximity to each other.
10. The sensor according to claim 9, wherein the third and fourth
MR elements are located in proximity to each other.
11. The sensor according to claim 1, wherein the magnetic field
sensing elements comprise MR elements couple in a bridge having
first and second pairs of MR elements, wherein the first and second
pairs of the MR elements are spaced apart less than a width of the
magnet.
12. The sensor according to claim 11, wherein the processing module
subtracts signals from the first pair of MR elements from signals
from the second pair of MR elements.
13. The sensor according to claim 1, wherein the processing module
includes a transfer function for airgap versus output signal,
wherein the transfer function includes a shape of the magnet.
14. The sensor according to claim 13, the shape of magnet includes
a curved surface.
15. The sensor according to claim 14, wherein the curved surface
comprises a convex shape.
16. The sensor according to claim 1, wherein the magnetic field
sensing elements comprise MR elements coupled in a bridge, wherein
each of the MR elements are substantially symmetric with respect to
each other.
17. A method, comprising: employing magnetic field sensing elements
coupled in a differential bridge; and employing a processing module
configured to receive signals from the bridge to determine a
distance from the magnetic field sensing elements to a magnet from
flux line divergence of magnetic flux generated by the magnet,
wherein an output signal corresponding to the determined distance
from the magnetic field sensing elements to the magnet is
substantially linear for a given airgap range.
18. The method according to claim 17, wherein the magnetic field
sensing elements comprise MR elements.
19. The method according to claim 17, wherein the magnetic field
sensing elements comprise GMR elements.
20. The method according to claim 17, wherein the magnetic field
sensing elements comprise Hall elements.
21. The method according to claim 17, further including a die,
wherein the magnetic field sensing elements are positioned in
relation to the die.
22. The method according to claim 21, wherein the magnetic field
sensing elements are located in a plane.
23. The method according to claim 22, wherein the bridge element
comprise elements L1, L2, R1, R2, and an output signal comprises
combining signals from L1, L2, R1, R2.
24. (canceled)
25. The method according to claim 17, wherein the magnetic field
sensing elements comprise first, second, third, and fourth MR
elements coupled in a bridge, wherein the first and second MR
elements are located in proximity to each other.
26. The method according to claim 25, wherein the third and fourth
MR elements are located in proximity to each other.
27. The method according to claim 17, wherein the magnetic field
sensing elements comprise MR elements coupled in a bridge having
first and second pairs of MR elements, wherein the first and second
pairs of the MR elements are spaced apart less than a width of the
magnet.
28. The method according to claim 27, wherein the processing module
subtracts signals from the first pair of MR elements from signals
from the second pair of MR elements.
29. The method according to claim 17, wherein the processing module
includes a transfer function for airgap versus output signal,
wherein the transfer function includes a shape of the magnet.
30. The method according to claim 29, the shape of magnet includes
a curved surface.
31. The method according to claim 30, wherein the curved surface
comprises a convex shape.
32. The method according to claim 17, wherein the magnetic field
sensing elements comprise MR elements coupled in a bridge, wherein
each of the MR elements are substantially symmetric with respect to
each other.
33. The method according to claim 17, wherein the processing module
includes a transfer function for airgap versus output signal,
wherein the transfer function includes a shape of the magnet, and
further including selecting the curve of the magnet to achieve
desired flux line divergence characteristics.
34. A magnet sensor IC package, comprising: means for magnetic
field sensing having elements coupled in a differential bridge; and
a means for processing for receiving signals from the bridge and
determining a distance from the magnetic field sensing elements to
a magnet from flux line divergence of magnetic flux generated by
the magnet, wherein an output signal corresponding to the
determined distance from the means for magnetic field sensing to
the magnet is substantially linear for a given airgap range.
35. The magnet sensor IC package according to claim 34, further
including a die, wherein the magnetic field sensing elements are
positioned in relation to the die.
36. The magnet sensor IC package according to claim 34, wherein the
bridge elements comprise elements L1, L2, R1, R2, and an output
signal comprises combining signals from L1, L2, R1, R2.
37. The magnet sensor IC package according to claim 34, wherein the
means for processing module includes a transfer function for airgap
versus output signal, wherein the transfer function includes a
shape of the magnet.
Description
BACKGROUND
[0001] Magnetic sensors are widely used in modern systems to
measure or detect physical parameters, such as magnetic field
strength, current, position, motion, orientation, and so forth.
There are many different types of sensors for measuring magnetic
fields and other parameters. However, such sensors suffer from
various limitations, for example, excessive size, inadequate
sensitivity dynamic range, cost, and/or reliability and the
like.
SUMMARY
[0002] The present invention provides method and apparatus for a
magnetic field sensor having magnetic field sensing elements for
measuring over distance, e.g., an airgap, the divergence of the
flux lines generated by a magnet. In embodiments, the direction of
the flux lines is determined with respect to a plane from which the
flux lines extend from the magnet. Linear sensors can be provided
by sensing the divergence of magnetic flux lines over an air gap
from the plane of the magnet.
[0003] Example sensor embodiments have enhanced performance (e.g.,
sensitivity and immunity to stray field) over a larger air gap
range, as compared to conventional sensors. Immunity to stray
fields may be achieved using a different bridge of MR elements due
to the symmetry of the flux lines generated by the magnet.
[0004] In one aspect, a sensor comprises: magnetic field sensing
elements coupled in a differential bridge; and a processing module
configured to receive signals from the bridge to determine a
distance from the magnetic field sensing elements to a magnet from
flux line divergence of magnetic flux generated by the magnet.
[0005] A sensor can further include one or more of the following
features: the magnetic field sensing elements comprise MR elements,
the magnetic field sensing elements comprise GMR elements, the
magnetic field sensing elements comprise Hall elements, a die,
wherein the magnetic field sensing elements are positioned in
relation to the die, the magnetic field sensing elements are
located in a plane, the bridge element comprise elements L1, L2,
R1, R2, and an output signal comprises combining signals from L1,
L2, R1, R2, an output signal corresponding to the determined
distance from the magnetic field sensing elements to the magnet is
substantially linear for a given airgap range, the magnetic field
sensing elements comprise first, second, third, and fourth MR
elements coupled in a bridge, wherein the first and second MR
elements are located in proximity to each other, the third and
fourth MR elements are located in proximity to each other, the
magnetic field sensing elements comprise MR elements couple in a
bridge having first and second pairs of MR elements, wherein the
first and second pairs of the MR elements are spaced apart less
than a width of the magnet, the processing module subtracts signals
from the first pair of MR elements from signals from the second
pair of MR elements, the processing module includes a transfer
function for airgap versus output signal, wherein the transfer
function includes a shape of the magnet, the shape of magnet
includes a curved surface, the curved surface comprises a convex
shape, the magnetic field sensing elements comprise MR elements
coupled in a bridge, and/or each of the MR elements are
substantially symmetric with respect to each other.
[0006] In another aspect, a method comprises: employing magnetic
field sensing elements coupled in a differential bridge; and
employing a processing module configured to receive signals from
the bridge to determine a distance from the magnetic field sensing
elements to a magnet from flux line divergence of magnetic flux
generated by the magnet.
[0007] A method can further include one or more of the following
features: the magnetic field sensing elements comprise MR elements,
the magnetic field sensing elements comprise GMR elements, the
magnetic field sensing elements comprise Hall elements, a die,
wherein the magnetic field sensing elements are positioned in
relation to the die, the magnetic field sensing elements are
located in a plane, the bridge element comprise elements L1, L2,
R1, R2, and an output signal comprises combining signals from L1,
L2, R1, R2, an output signal corresponding to the determined
distance from the magnetic field sensing elements to the magnet is
substantially linear for a given airgap range, the magnetic field
sensing elements comprise first, second, third, and fourth MR
elements coupled in a bridge, wherein the first and second MR
elements are located in proximity to each other, the third and
fourth MR elements are located in proximity to each other, the
magnetic field sensing elements comprise MR elements couple in a
bridge having first and second pairs of MR elements, wherein the
first and second pairs of the MR elements are spaced apart less
than a width of the magnet, the processing module subtracts signals
from the first pair of MR elements from signals from the second
pair of MR elements, the processing module includes a transfer
function for airgap versus output signal, wherein the transfer
function includes a shape of the magnet, the shape of magnet
includes a curved surface, the curved surface comprises a convex
shape, the magnetic field sensing elements comprise MR elements
coupled in a bridge, and/or each of the MR elements are
substantially symmetric with respect to each other.
[0008] In a further aspect, a magnet sensor IC package comprises:
means for magnetic field sensing having elements coupled in a
differential bridge; and a means for processing for receiving
signals from the bridge and determining a distance from the
magnetic field sensing elements to a magnet from flux line
divergence of magnetic flux generated by the magnet. An IC package
can further include a die, wherein the magnetic field sensing
elements are positioned in relation to the die. An IC package can
further include the bridge elements having elements L1, L2, R1, R2,
and an output signal combining signals from L1, L2, R1, R2. An IC
package can further include that the means for processing module
includes a transfer function for airgap versus output signal,
wherein the transfer function includes a shape of the magnet.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The foregoing features of this invention, as well as the
invention itself, may be more fully understood from the following
description of the drawings in which:
[0010] FIG. 1 is a block diagram of a sensor detecting magnetic
flux line divergence for determining an airgap;
[0011] FIG. 1A shows an example representation of an sensor IC
package having an airgap with a magnet;
[0012] FIG. 2 is a schematic representation of sensor having a
sensing element bridge;
[0013] FIG. 3 is a circuit diagram showing the bridge element
connection for the bridge of FIG. 2;
[0014] FIG. 4 is a schematic representation of flux line divergence
for an example magnet;
[0015] FIG. 5 shows an example representation of tangent lines for
flux lines shown in FIG. 4;
[0016] FIG. 6 is an example plot of a sensing element output signal
versus airgap;
[0017] FIGS. 7A and 7B show example plots of MR-based sensing
element output signal data with and without a common mode field for
sensor displacement;
[0018] FIG. 8 is an example plot of sensing element output signal
data for a Hall element based sensor embodiment;
[0019] FIG. 9 is an example plot showing example maximum position
error for MR and Hall-based sensor embodiments; and
[0020] FIG. 10 is a schematic representation of an example computer
that can perform at least a portion of the processing described
herein.
DETAILED DESCRIPTION
[0021] FIG. 1 shows an example sensor 100 having a magnetic field
sensing element 102 positioned in relation to a magnet 104. A
signal processing module 106 is coupled to the magnetic field
sensing element 102 for processing an output signal of the magnetic
field sensing element. In embodiments, the magnetic field sensing
element 102 can include magnetoresistive (MR) elements coupled in a
bridge configuration, for example. In other embodiments, Hall
elements are used. An output module 108 can be coupled to the
signal processing module 106 for generating an output signal, such
as the output signal on an IO pin of an integrated circuit package.
As described more fully below, for a given range in airgap between
the magnet 104 and the sensing element 102, an output signal can be
substantially linear.
[0022] FIG. 1A shows an example sensor IC package 150 having a
variable air gap with respect to a magnet 152. As described more
fully, below the sensor 150 can provide an output signal
corresponding to the airgap between the IC package/sensors and the
magnet.
[0023] FIG. 2 shows an example embodiment of a magnetic field
sensing element 200 provided as magnetoresistive (MR) elements L1,
L2, R1, R2 coupled in a bridge configuration positioned in relation
to a die 201 and a planar surface 202 of a magnet 204. The bridge
elements L1, L2, R1, R2 are in, on, or about the die 201. In
embodiments, MR elements L1 and L2 are as close together as
possible and MR elements R1 and R2 are as close together as
possible. The length of each yoke may be limited to avoid averaging
over distance which may impact accuracy). In embodiments, bridge
spacing (distance between L1, L2 and R1, R2) should be selected as
not too small (to avoid decreasing sensitivity) and not larger than
the magnet width).
[0024] FIG. 3 shows an example circuit implementation of a bridge
in which MR elements L1, L2, R1, R2 are coupled to a reference REF,
such as ground. In the illustrated embodiment, L refers to left and
R refers to right in the example physical bridge configuration and
should not be considered limiting any way. In embodiments, a
differential measurement of the bridge is used for which an example
transfer function is shown in FIG. 6. This transfer function
depends upon the magnet shape, and thus, should be calibrated for
the magnet in the application.
[0025] It is understood that magnetoresistance refers to the
dependence of the electrical resistance of a sample on the strength
of external magnetic field characterized as:
.delta..sub.H=[R(0)-R(H)]/R(0)
where R(H) is the resistance of the sample in a magnetic field H,
and R(0) corresponds to H=0. The term "giant magnetoresistance"
indicates that the value .delta..sub.H for multilayer structures
significantly exceeds the anisotropic magnetoresistance, which has
a typical value within a few percent.
[0026] Giant magnetoresistance (GMR) is a quantum mechanical
magnetoresistance effect observed in thin-film structures composed
of alternating ferromagnetic and non-magnetic conductive layers.
The effect is observed as a significant change in the electrical
resistance depending on whether the magnetization of adjacent
ferromagnetic layers are in a parallel or an antiparallel
alignment. The overall resistance is relatively low for parallel
alignment and relatively high for antiparallel alignment. The
magnetization direction can be controlled, for example, by applying
an external magnetic field. The effect is based on the dependence
of electron scattering on the spin orientation. A bridge of four
identical GMR devices is insensitive to a uniform magnetic field
and is reactive when the field directions are antiparallel in the
neighboring arms of the bridge.
[0027] It is understood that the bridge elements can be configured
in any practical arrangement to meet the needs of a particular
application without departing from the scope of the claimed
invention.
[0028] Referring again to FIG. 2, in the illustrated embodiment,
the left bridge elements L1, L2 are positioned together and the
right bridge elements R1, R2 are positioned together. In
embodiments, the bridge elements L1, L2, R1, R2, are formed in or
about a semiconductor die 201. Reference arrow REF shows the axis
of sensitivity for the sensor along the X axis in the plane of the
die 201. Bridge elements R1, R2 see signals parallel to the
reference plane (X axis in the illustrated embodiment) and bridge
elements L1, L2, see signals anti-parallel to the reference plane.
In an example embodiment, the right element R1, R2 signals are
subtracted from the left element L1, L2 signals, as described more
fully below. Stray fields are rejected since the left and right
elements see opposing signals.
[0029] In example embodiments, the left pair of bridge elements L1,
L2 is positioned an equal distance from the right pair of bridge
elements R1, R2 with respect to an axis AX extending
perpendicularly from a center of the planar surface 202 of the
magnet 204. It will be appreciated that for perfectly symmetrical
placement of the bridge elements L1, L2, R1, R2 with respect to
each other and the magnet planar surface, the flux lines seen by
the left and right bridge elements will be the same magnitude in an
ideal system. In embodiments, for a given airgap range the sensor
output will be substantially linear, as described more fully
below.
[0030] FIG. 4 shows flux lines 400a-f generated from a planar
surface 402 of a magnet 404 shown having a north pole 406 and a
south pole 408. In the illustrated embodiment, the flux lines 400
are shown exiting the north pole 406 of the magnet. The flux lines
400 are shown in symmetric pairs, e.g., first pair 400a, b, second
pair 400c, d, and third pair 400e, f. Each of the flux lines 400 is
shown having a respective tangent arrow 401a-f corresponding to a
given distance from the plane of the magnet. As can be seen, in the
illustrated embodiment, the tangent arrows 401 for each pair of
flux lines 400 is symmetric about an axis 403 perpendicular to the
planar surface 402 of the magnet. For example, tangent arrows 401a,
401b for the first pair of flux lines are symmetrical about the
axis 403 extending perpendicularly from the planar surface 402 of
the magnet, as shown more clearly in FIG. 5. In embodiments, the
axis 403 is located in a center of the magnet planar surface 402
corresponding to symmetric flux line pairs.
[0031] As can be seen, the orientation of the magnetic flux lines
400 and tangent arrows 401 changes with a distance from the planar
surface 402 of the magnet. Since the flux lines 400 are symmetric
about the axis 402, the magnetic field sensing elements (e.g., L1,
L2, R1, R2 of FIG. 2) can be assembled in a differential bridge,
for example, to measure the angles of the flux lines.
[0032] In an example embodiment, a GMR element comprises a double
pinned stack with a 1000e bias parallel to the magnetization of the
magnet and a bridge biased with 2.8V. It is understood that a
variety of GMR element configuration and characteristics can be
used to meet the needs of a particular application without
departing from the scope of the claimed invention.
[0033] FIG. 6 shows example data for a GMR sensor over a
3.8.times.3.8.times.2.75 mm NdFeB magnet where a signal level in mV
is shown versus air gap in mm, where the air gap is the distance
between the package and the magnet. A first set of dots 600
represents an output signal when no common mode field is applied.
As can be seen, a generally linear response is defined by the first
set of dots. A second set of dots 602 represents an output signal
when a 200e field is applied in X, -X, Y and -Y directions with
respect to a plane of the die (see FIG. 2), where X is the
reference direction. The plots show the dependence of the signal
over placement of the sensor.
[0034] FIG. 7A shows example sensor data for X axis displacement
where a first set of dots 700 correspond to no applied common mode
field and a second set of dots 702 correspond to an applied field
of 20 Oe in X, -X, Y, and -Y directions and FIG. 7B shows Y axis
displacement data. FIGS. 7A and 7B show dependence of the signal
over placement of the sensor. Misplacement refers to when the
sensor is not placed in the center of the magnet. For example, a
pure X misplacement is when the axis 403 is still in the plane of
the die but not centered on the bridge. A pure Y misplacement is
when the axis 403 is not in the plane of die any more but is in the
median plane of the bridge.
[0035] As can be seen, sensitivity of a GMR-based sensor is lower
at small air gaps and higher at intermediate air gaps. In addition,
immunity to stray fields is better for GMR as compared to Hall
effect sensing elements for air gap higher than 4 mm, for example,
in illustrative embodiments.
[0036] In embodiments, the magnet can be shaped to engineer the
divergence of the flux lines to meet the needs of a particular
application. For example, the magnet may have a convex shape so
that an increase in flux divergence at smaller distances may be
achieved. Concave magnet shapes can be also be used. In
embodiments, the curve of the magnet can be selected to achieve
desired flux line divergence characteristics. Example curves can be
defined by various functions, such as hyperbolic, eccentric,
circular, parabolic, exponential, polygonal, and the like.
[0037] FIG. 8 shows example magnetic sensing element output signal
data represented as a first set of dots 800 for a Hall element
versus air gap in mm. As can be seen the Hall output data 800 is
generally decreasing exponentially. A second set of dots represents
the output signal in the presence of a common mode (stray) field of
about 20 Oe applied in the Z and -Z direction (out of the plane of
the die). In the illustrated embodiment, the Y-axis is log
scale.
[0038] FIG. 9 shows an example maximum error position of an
illustrative GMR-based sensor and a Hall-based sensor with applied
common mode field of about 20 Oe. As can be seen, the GMR-based
sensor embodiments retain accuracy over a larger air gap range than
the Hall-based sensor embodiments.
[0039] Embodiments of the invention are useful for a wide range of
sensing applications including wheel speed, engine sensors,
transmission sensors and speed sensing in general here a ring
magnet is used.
[0040] As used herein, the term "magnetic field sensing element" is
used to describe a variety of electronic elements that can sense a
magnetic field. The magnetic field sensing element can comprise,
but is not limited to, a Hall Effect element, a magnetoresistance
element, and/or a magnetotransistor. As is known, there are
different types of Hall Effect elements, for example, a planar Hall
element, a vertical Hall element, and a Circular Vertical Hall
(CVH) element. As is also known, there are different types of
magnetoresistance elements, for example, a semiconductor
magnetoresistance element such as Indium Antimonide (InSb), a giant
magnetoresistance (GMR) element, for example, a spin valve, an
anisotropic magnetoresistance element (AMR), a tunneling
magnetoresistance (TMR) element, a magnetic tunnel junction (MTJ),
and a spin-valve. The magnetic field sensing element may be a
single element or, alternatively, may include two or more magnetic
field sensing elements arranged in various configurations, e.g., a
half bridge or full bridge. Depending on the device type and other
application requirements, the magnetic field sensing element may be
a device made of a type IV semiconductor material such as Silicon
(Si) or Germanium (Ge), or a type III-V semiconductor material like
Gallium-Arsenide (GaAs) or an Indium compound, e.g.,
Indium-Antimonide (InSb).
[0041] As is known, some of the above-described magnetic field
sensing elements tend to have an axis of maximum sensitivity
parallel to a substrate that supports the magnetic field sensing
element, and others of the above-described magnetic field sensing
elements tend to have an axis of maximum sensitivity perpendicular
to a substrate that supports the magnetic field sensing element. In
particular, planar Hall elements tend to have axes of sensitivity
perpendicular to a substrate, while metal based or metallic
magnetoresistance elements (e.g., GMR, TMR, AMR) and vertical Hall
elements tend to have axes of sensitivity parallel to a
substrate.
[0042] As used herein, the term "magnetic field sensor" is used to
describe a circuit that uses a magnetic field sensing element,
generally in combination with other circuits. Magnetic field
sensors are used in a variety of applications, including, but not
limited to, an angle sensor that senses an angle of a direction of
a magnetic field, a current sensor that senses a magnetic field
generated by a current carried by a current-carrying conductor, a
magnetic switch that senses the proximity of a ferromagnetic
object, a rotation detector that senses passing ferromagnetic
articles, for example, magnetic domains of a ring magnet or a
ferromagnetic target (e.g., gear teeth) where the magnetic field
sensor is used in combination with a back-biased or other magnet,
and a magnetic field sensor that senses a magnetic field density of
a magnetic field.
[0043] FIG. 10 shows an exemplary computer 1000 that can perform at
least part of the processing described herein. The computer 1000
includes a processor 1002, a volatile memory 1004, a non-volatile
memory 1006 (e.g., hard disk), an output device 1007 and a
graphical user interface (GUI) 1008 (e.g., a mouse, a keyboard, a
display, for example). The non-volatile memory 1006 stores computer
instructions 1012, an operating system 1016 and data 1018. In one
example, the computer instructions 1012 are executed by the
processor 1002 out of volatile memory 1004. In one embodiment, an
article 1020 comprises non-transitory computer-readable
instructions.
[0044] Processing may be implemented in hardware, software, or a
combination of the two. Processing may be implemented in computer
programs executed on programmable computers/machines that each
includes a processor, a storage medium or other article of
manufacture that is readable by the processor (including volatile
and non-volatile memory and/or storage elements), at least one
input device, and one or more output devices. Program code may be
applied to data entered using an input device to perform processing
and to generate output information.
[0045] The system can perform processing, at least in part, via a
computer program product, (e.g., in a machine-readable storage
device), for execution by, or to control the operation of, data
processing apparatus (e.g., a programmable processor, a computer,
or multiple computers). Each such program may be implemented in a
high level procedural or object-oriented programming language to
communicate with a computer system. However, the programs may be
implemented in assembly or machine language. The language may be a
compiled or an interpreted language and it may be deployed in any
form, including as a stand-alone program or as a module, component,
subroutine, or other unit suitable for use in a computing
environment. A computer program may be deployed to be executed on
one computer or on multiple computers at one site or distributed
across multiple sites and interconnected by a communication
network. A computer program may be stored on a storage medium or
device (e.g., CD-ROM, hard disk, or magnetic diskette) that is
readable by a general or special purpose programmable computer for
configuring and operating the computer when the storage medium or
device is read by the computer. Processing may also be implemented
as a machine-readable storage medium, configured with a computer
program, where upon execution, instructions in the computer program
cause the computer to operate.
[0046] Processing may be performed by one or more programmable
processors executing one or more computer programs to perform the
functions of the system. All or part of the system may be
implemented as, special purpose logic circuitry (e.g., an FPGA
(field programmable gate array) and/or an ASIC
(application-specific integrated circuit)).
[0047] Having described exemplary embodiments of the invention, it
will now become apparent to one of ordinary skill in the art that
other embodiments incorporating their concepts may also be used.
The embodiments contained herein should not be limited to disclosed
embodiments but rather should be limited only by the spirit and
scope of the appended claims. All publications and references cited
herein are expressly incorporated herein by reference in their
entirety.
[0048] Elements of different embodiments described herein may be
combined to form other embodiments not specifically set forth
above. Various elements, which are described in the context of a
single embodiment, may also be provided separately or in any
suitable subcombination. Other embodiments not specifically
described herein are also within the scope of the following
claims.
* * * * *